I assume the 35.5 knots was a peak speed. I don't know, but whatever it was it won the competition so it must have been verified in some way.
I doubt the video footage is of the actual speed runs (looks like beating upwind on port). My guess is that was just the best footage as he was near the camera and the actual speeds were done on water that was flatter and further away.
Anyway I just thought it was fun and a crazy idea to do speed on a Go board. Not sure who's idea that was ( I know Ian had ideas about making a Futura go 40 knots). So enjoy the video and if you think you can go faster then go prove it!